Fabrication method for semiconductor integrated circuit devices and semiconductor integrated circuit device

ABSTRACT

To improve a shape of a gate electrode having SiGe, after patterning a gate electrode  15 G having an SiGe layer  15   b  by a dry etching process, a plasma processing (postprocessing) is carried out in an atmosphere of an Ar/CHF 3  gas. Thereby, the gate electrode  15 G can be formed without causing side etching at two side faces (SiGe layer  15   b ) of the gate electrode  15 G.

[0001] This application is a Divisional application of application Ser. No. ______ (Attorney Docket No. 501.39812X00, entitled “FABRICATION METHOD FOR SEMICONDUCTOR INTEGRATED CIRCUIT DEVICES AND SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE”), filed Mar. 19, 2001.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a technology of a fabrication method for semiconductor integrated circuit devices and a semiconductor integrated circuit device, particularly to a technology effectively applied to a fabrication method for semiconductor integrated circuit devices and a semiconductor integrated circuit device having an alloy of silicon (Si) and germanium (Ge) (hereinafter, simply referred to as SiGe) of polycrystal or single crystal.

[0003] With regard to a technology of a semiconductor integrated circuit device using SiGe for a gate electrode material, there are descriptions in, for example, J. Vac. Sci. Technol July/August 1997 p1874 through p1880, J. Vac. Sci. Technol July/August 1998 p1833 through p1840 and Japanese Patent Laid-Open No. 330463/1999, disclosing a technology of patterning an SiGe gate electrode.

SUMMARY OF THE INVENTION

[0004] A description will be given of a result of investigating a technology of forming a gate electrode having an SiGe layer by the inventors as follows.

[0005] A processing of forming a gate electrode having an SiGe layer includes three processing steps of depositing a gate electrode forming film, patterning thereof and a postprocessing thereof. That is, first, after forming a gate insulating film over a main face of a semiconductor substrate, a gate electrode forming film having an SiGe layer is deposited thereabove. Successively, after forming a photoresist pattern over the gate electrode forming film, a gate electrode having the SiGe layer is formed by patterning the gate electrode forming film by using an etching gas including, for example, chlorine (Cl₂) and bromine (Br) with the photoresist pattern as an etching mask. Thereafter, in order to remove Cl, Br and reaction products including thereof and reaction products including Si adhered to a surface of the semiconductor substrate in forming the gate electrode (hereinafter, also referred to as adhered matters), a plasma processing is carried out to the semiconductor substrate in an atmosphere of a predetermined gas (postprocessing).

[0006] The postprocessing is a processing which is also carried out after forming the gate electrode by patterning polycrystal silicon and when the postprocessing is not carried out, there causes a drawback, for example, as follows. That is, when the reaction products are not removed, occurrence of foreign matters is caused and reliability or yield of the semiconductor integrated circuit device is deteriorated. When the adhered matters are adhered to a main face of other semiconductor substrate before patterning the gate electrode, in patterning the gate electrode of the other semiconductor substrate, the adhered matters constitute a mask and there is produced etching residue of a gate electrode material. Further, when Cl or Br adhered to the surface of the semiconductor substrate is not removed, parts of a semiconductor fabricating apparatus are corroded by Cl or Br. Further, Cl or Br is toxic and therefore, adverse influence is effected on the human body.

[0007] With regard to a gas in the postprocessing when SiGe is used as the gate electrode material, there is used, for example, O₂/CHF₃ since a stable electricity discharge range is provided, further, the gas is generally used in the postprocessing when polycrystal silicon is used as a gate electrode material, an amount of data is enormous and introduction thereof is facilitated. Similar to the postprocessing when the polycrystal silicon is used as a gate electrode material.

[0008] However, according to the technology of forming the gate electrode having the SiGe layer, it has been found for the first time by experiment and evaluation of the inventors that there poses the following problem.

[0009] That is, there poses a problem that so-to-speak side etching is caused such that two side faces of the SiGe layer portion in the gate electrode are polished toward the center.

[0010] First, when the inventors have evaluated performance of etching SiGe, it has been that the side etching is liable to cause. Hence, when evaluation has been carried out further in detail, it has been found that although the side etching is not caused in a processing at an etching chamber, the side etching is caused when the postprocessing is carried out at a post processing chamber. Further, it has also been found that presence or absence of occurrence of the side etching is dependent upon a concentration of Ge. Further, a shape of the side etching has not been improved even after investigating a reduction in a concentration of CHF₃ or a reduction in electricity discharge power at the postprocessing.

[0011] It is an object of the invention to provide a technology capable of improving a shape of a gate electrode having SiGe.

[0012] It is other object of the invention to provide a technology capable of promoting an accuracy of dimensions of fabricating a gate electrode having SiGe.

[0013] Further, it is other object of the invention to provide a technology capable of promoting yield of a semiconductor integrated circuit device having a gate electrode having SiGe.

[0014] Further, it is other object of the invention to provide a technology capable of promoting function of a semiconductor integrated circuit having a gate electrode having SiGe.

[0015] Further, it is other object of the invention to provide a technology capable of simplifying fabrication steps of a semiconductor integrated circuit device having a gate electrode having SiGe.

[0016] Further, it is other object of the invention to provide a technology capable of shortening development and fabrication time period of a semiconductor integrated circuit device having a gate electrode having SiGe.

[0017] The above-described and other objects and novel characteristics of the invention will become apparent from description of the specification and attached drawings.

[0018] A simple explanation will be given of an outline of representative aspects of the invention disclosed in the application as follows.

[0019] That is, according to an aspect of the invention, there are provided steps of forming a gate electrode having an SiGe layer over a semiconductor substrate by patterning a gate electrode forming film having the SiGe layer and thereafter subjecting the semiconductor substrate to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a second gas having a function of etching Si.

[0020] Further, according to another aspect of the invention, there are provided steps of forming a gate electrode over a semiconductor substrate by patterning a gate electrode forming film deposited on the semiconductor substrate and thereafter subjecting the semiconductor substrate to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a second gas having a function of etching Si and the step of depositing the gate electrode forming film includes a step of depositing an SiGe layer and a step of depositing a polycrystal silicon layer at a layer upward from the SiGe layer.

[0021] Further, according to another aspect of the invention, there are further provided after the plasma processing, a step of forming side wall insulating films at side faces of the gate electrode, a step of exposing an upper face of the gate electrode and portions of a main face of the semiconductor substrate, a step of depositing a metal film having a high melting point over the semiconductor substrate and a step of forming a metal silicide layer having a high melting point at the upper face of the gate electrode and the portions of the main face of the semiconductor substrate.

[0022] Further, according to another aspect of the invention, the metal silicide layer having the high melting point is made of cobalt silicide.

[0023] Further, according to another aspect of the invention, there are provided steps of forming a gate electrode over a semiconductor substrate by patterning a gate electrode forming film deposited over the semiconductor substrate and thereafter subjecting the semiconductor substrate to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a second gas having a function of etching Si and the step of depositing the gate electrode forming film includes a step of depositing an SiGe layer and a step of depositing a metal layer at a layer upward from the SiGe layer.

[0024] Further, according to another aspect of the invention, there is further provided a step of introducing boron to the SiGe layer.

[0025] Further, according to another aspect of the invention, the first gas is constituted by an inert gas.

[0026] Further, according to another aspect of the invention, the first gas is constituted by Ar, He, Kr or Xe.

[0027] Further, according to another aspect of the invention, the first gas is constituted by nitrogen gas.

[0028] Further, according to another aspect of the invention, the second gas is constituted by a gas including fluorine.

[0029] Further, according to another aspect of the invention, the second gas is constituted by CHF₃, CF₄, C₂F₆ or SF₆.

[0030] Further, according to another aspect of the invention, when the first gas is constituted by Ar gas, pressure in the atmosphere is made equal to or smaller than 70 Pa.

[0031] Further, according to another aspect of the invention, when the first gas is constituted by Ar gas, a microwave power for forming a plasma is made 750 W.

[0032] Further, according to another aspect of the invention, when the first gas is constituted by Ar gas and the second gas is constituted by CHF₃, a concentration of the second gas is made equal to or smaller than 5% of a total.

[0033] Further, according to another aspect of the invention, when the gate electrode forming film having the SiGe layer is patterned, there is carried out a plasma etching processing in an atmosphere of chlorine, bromine or a mixed gas of these.

[0034] Further, according to another aspect of the invention, a concentration of Ge of the SiGe layer is made equal to or larger than 10% of a total.

[0035] Further, according to another aspect of the invention, the concentration of Ge of the SiGe layer is made equal to or larger than 20% of the total.

[0036] Further, according to another aspect of the invention, the concentration of Ge of the SiGe layer is made equal to or larger than 40% of the total.

[0037] Further, according to another aspect of the invention, there is further provided a step of fabricating a semiconductor integrated circuit device in which the semiconductor substrate after the step of patterning the gate electrode is transferred to the plasma processing step in a state of maintaining a vacuum state.

[0038] Further, according to another aspect of the invention, a side etching amount at two side faces of the gate electrode after the plasma processing is made equal to or smaller than 40% of a length in a channel length direction of the gate electrode at a portion thereof other than the SiGe layer.

[0039] Further, according to another aspect of the invention, a length in the channel direction of the gate electrode at the SiGe layer after the plasma processing, is equal to the length in the channel length direction of the gate electrode at the portion other than the SiGe layer.

[0040] Further, according to another aspect of the invention, there is used a gate electrode of an n-channel type field effect transistor or a p-channel type field effect transistor formed on the same semiconductor substrate for the gate electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is an explanatory view of an etching apparatus used for a fabrication method of semiconductor integrated circuit devices according to an embodiment of the invention;

[0042]FIG. 2 is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device according to the embodiment of the invention;

[0043]FIG. 3 is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 2;

[0044]FIG. 4A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 3 and

[0045]FIG. 4B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 4A;

[0046]FIG. 5A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 4A and

[0047]FIG. 5B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 5A;

[0048]FIG. 6A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 5A and

[0049]FIG. 6B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 6A;

[0050]FIG. 7A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 6A and

[0051]FIG. 7B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 7A;

[0052]FIG. 8A is a partial sectional view of a semiconductor substrate after a postprocessing for explaining a problem of a technology investigated by the inventors for carrying out the invention and

[0053]FIG. 8B is a sectional view enlarging essential portions of FIG. 8A;

[0054]FIG. 9A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 7A and

[0055]FIG. 9B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 9A;

[0056]FIG. 10 is a graph diagram showing a result of investigating whether Cl, Br or the like adhered to the semiconductor substrate has been removed by the postprocessing of the invention by total reflection type fluorescent X-ray;

[0057]FIG. 11A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 9A and

[0058]FIG. 11B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 11A;

[0059]FIG. 12A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 11A and

[0060]FIG. 12B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 12A;

[0061]FIG. 13A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 12A and

[0062]FIG. 13B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 13A;

[0063]FIG. 14A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 13A and

[0064]FIG. 14B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 14A;

[0065]FIG. 15 is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 14A;

[0066]FIG. 16A is a sectional view of essential portions in a fabrication step of a semiconductor integrated circuit device according to other embodiment of the invention and

[0067]FIG. 16B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 16A;

[0068]FIG. 17A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 16A and

[0069]FIG. 17B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 17A;

[0070]FIG. 18A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 17A and

[0071]FIG. 18B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 18A;

[0072]FIG. 19A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 18A and

[0073]FIG. 19B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 19A;

[0074]FIG. 20A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 19A and

[0075]FIG. 20B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 20A;

[0076]FIG. 21A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 20A and

[0077]FIG. 21B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 21A; and

[0078]FIG. 22A is a sectional view of essential portions in a fabrication step of the semiconductor integrated circuit device continuous to FIG. 21A and

[0079]FIG. 22B is a sectional view enlarging essential portions of an area of forming n-channel type MISFET of FIG. 22A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0080] In explaining embodiments of the invention, a semiconductor wafer (semiconductor substrate) refers to a silicon single crystal substrate (generally, substantially in a planer circle shape) used in fabrication of a semiconductor integrated circuit, a sapphire substrate, a glass substrate, other insulating, noninsulating or semiconductor substrate as well as a substrate of a composite of these. Further, in the application, a semiconductor device includes a semiconductor device formed on a semiconductor or an insulating substrate such as a silicon wafer or a sapphire substrate as well as, a semiconductor device formed on other insulating substrate of glass or the like such as TFT (Thin-Film-Transistor) and STN (Super-Twisted Nematic) liquid crystal except a case particularly specified otherwise.

[0081] Although in the following embodiments, as necessary for convenience, an explanation will be given of the following embodiments divided into a plurality of sections or embodiments, except a case particularly specified, these are not unrelated to each other but one of them is under a relationship of modified examples, detailed or supplemental descriptions of a portion or a total of other thereof.

[0082] Further, in the following embodiments, when a number of elements (including number of pieces, numerical value, amount, or range) is referred to, except a case particularly specified and a case in which the number is limited to a specific number clearly as a principle, the number is not limited to the specific number but may be equal to or larger than or equal to or smaller than the specific number.

[0083] Further, in the following embodiments, a constituent element (including element step) is not naturally indispensable necessarily except a case particularly specified and a case regarded as clearly indispensable.

[0084] Similarly, in the following embodiments, when a shape or a positional relationship of a constituent element is referred, except a case particularly specified and a case regarded otherwise clearly as a principle, a constituent element having a shape substantially proximate or similar to the shape is included. This goes the same with the numerical value and the range.

[0085] Further, portions having the same functions in all the drawings for explaining the embodiments are attached with the same notations and repetitive explanation thereof will be omitted.

[0086] Further, according to the embodiments, MISFET (Metal Insulator Semiconductor Field Effect Transistor) representing a field effect transistor is abbreviated simply as MIS, MISFET of p-channel type is abbreviated as pMIS and MISFET of n-channel type is abbreviated as nMIS.

[0087] A detailed explanation will be given of embodiments of the present invention in reference to the drawings as follows.

[0088] (Embodiment 1)

[0089]FIG. 1 exemplifies a constitution of an etching apparatus 1 used in a fabrication method of a semiconductor integrated circuit device according to Embodiment 1.

[0090] The etching apparatus 1 is an apparatus for carrying out a series of processings for patterning a wiring forming film having an SiGe layer into a predetermined shape. A semiconductor wafer to be subjected to an etching processing is mounted to an arbitrary location of wafer cassette bases 2 a through 2 c. The semiconductor wafer at the wafer cassette bases 2 a through 2 c is transferred to an alignment unit 4 by an atmospheric transfer robot 3. At the alignment unit 4, aligning of a direction of a notch or an orientation flat of the semiconductor wafer is carried out. The semiconductor wafer finished with the alignment processing is transferred to a load/lock chamber 5 again by the atmospheric transfer robot 3. Vacuuming is carried out in the load/lock chamber 5 when the semiconductor wafer is transferred therein. When vacuuming at inside of the load/lock chamber 5 has been finished, the semiconductor wafer passes through a vacuum transfer chamber 7 and is transferred into an etching chamber 8 by a vacuum transfer robot 6. Further, a vacuum state is maintained in the vacuum transfer chamber 7.

[0091] In the etching chamber 8, a wiring forming film having an SiGe layer is patterned to a predetermined shape by, for example, a plasma dry etching processing. As an electricity discharge system in the etching chamber 8, there can be used all of electricity discharge systems such as ECR (Electron Cyclotron Resonance), RIE (Reactive Ion Etching), two frequency RIE, magnetron RIE and ICP (Inductively Coupled Plasma). Etching gas is produced by a single gas or a mixed gas of Cl₂, HBr, O₂ as explained later in detail. At a first step of etching processing, there is used a single gas of Cl₂ having a low selection ratio with regard to a silicon oxide film (SiO₂) and at and after a second step, there is a gas, for example, HBr/Cl₂ or HBr/Cl₂/O₂ to provide an anisotropic shape. At a terminal point detecting step and an overetching step of the etching processing, there is used a gas having a high selection ratio with regard to a silicon oxide film such as HBr/O₂ or Cl₂/O₂.

[0092] The semiconductor wafer finished with the etching processing passes through the vacuum transfer chamber 7 and is transferred into a postprocessing chamber 9 again by the vacuum transfer robot 6. That is, the semiconductor wafer after the etching processing is transferred into the postprocessing chamber 9 while maintaining the vacuum state without being brought into contact with the outer air. In the postprocessing chamber 9, a plasma processing is carried out to the semiconductor wafer as is explained later in detail. With regard to the electricity discharge system of the postprocessing chamber 9, similar to the etching chamber 8, there can be used all of discharge systems such as ECR, RIE, two frequency RIE, magnetron RIE or ICP. The semiconductor wafer finished with the postprocessing is transferred to an unload/unlock chamber 10 again by the vacuum transfer robot 6 and is returned to the wafer cassette bases 2 a through 2 c by the atmospheric transfer robot 3.

[0093] Next, in Embodiment 1, an explanation will be given of a case of applying the invention to, for example, a system LSI (Large Scale Integrated Circuit) having a logic circuit and a memory circuit on the same semiconductor substrate in reference to FIG. 2 through FIG. 15. Further, FIG. 4B through FIG. 9B and FIG. 11B through FIG. 15B are sectional views enlarging essential portions of an NMIS forming area of FIGS. 4A through FIG. 9A and FIGS. 11A through FIG. 15A. A gate electrode structure of a PMIS forming area is the same as a gate electrode structure of the nMIS forming area and accordingly, illustration thereof are omitted. Further, FIG. 8 is a view for explaining a problem of a technology investigated by the inventors for carrying out the invention.

[0094] First, as shown by FIG. 2, there is prepared a semiconductor substrate 11S comprising, for example, p-type single crystal silicon. The semiconductor substrate 11S at this stage is a semiconductor thin plate having a planar circle shape of about, for example, 8 inch (=about 20 cm), called as a semiconductor wafer. There are formed grooves 12 a having a depth of about 300 through 400 nm at a main face of the semiconductor substrate 11S. The groove 12 a is formed by covering an element forming area of the semiconductor substrate 11S with a silicon nitride film and thereafter subjecting the semiconductor substrate 11 at an element separating area to dry etching with the silicon nitride film as a mask.

[0095] Successively, by depositing a silicon oxide film having a film thickness of, for example, about 600 nm over the semiconductor substrate 11S including inner portions of the grooves 12 a by a CVD (Chemical Vapor Deposition) process and thereafter leaving the silicon oxide film only at the inner portions of the grooves 12 a by polishing the silicon oxide film by a CMP (Chemical Mechanical Polishing) process, at the element separating area of the semiconductor substrate 11S, there is formed an element separating portion 12 (trench isolation) of, for example, a groove type and an active area is formed at the element forming area surrounded thereby in plane view.

[0096] Thereafter, as shown by FIG. 3, at an NMIS forming area of the semiconductor substrate 11S, a p-type well 13P is formed by ion-implanting, for example, boron thereto and at a pMIS forming area, an n-type well 13N is formed by ion-implanting, for example, phosphor thereto. Further, at this occasion, at the nMIS forming area, an impurity (for example, boron) for controlling threshold voltage of the nMIS is ion-implanted thereto and at the pMIS forming area, an impurity (for example, phosphor) for controlling threshold voltage of the pMIS is ion-implanted.

[0097] Next, by cleaning respective surfaces of the p-type well 13P and the n-type well 13N by using a cleaning solution of HF (hydrofluoric acid) species and thereafter subjecting the semiconductor substrate 11S to wet oxidation at an elevated temperature of, for example, about 850° C., clean gate insulating films 14 each comprising a silicon oxide film are formed on the respective surfaces of the p-type well 13P and the n-type well 13N. The film thickness of the gate insulating film 14 is made, for example, equal to or smaller than 3 nm, for example, about 2.5 nm. Further, the film thickness of the gate insulating film 14, mentioned here, is a film thickness converted into that of a silicon dioxide film and may not be coincide with an actual film thickness.

[0098] The gate insulating film 14 may be constituted by a silicon oxynitride film in place of the silicon oxide film. That is, when the film thickness of the gate insulating film 14 is thinned, as described later, a portion of an impurity (boron) in an SiGe layer constituting a portion of a gate electrode by a heat treatment in processing, penetrates the gate insulating film 14 and is diffused into the semiconductor substrate 11S and threshold voltage becomes liable to vary. In comparison with the silicon oxide film, the impurity is difficult to penetrate the silicon oxynitride film and accordingly, by constituting the gate insulating film 14 by the silicon oxynitride film, the threshold voltage can be restrained from varying. Further, according to the silicon oxynitride film, in comparison with the silicon oxide film, there is provided a high effect of restraining occurrence of interfacial level or reducing electron trap in the film and accordingly, hot-carrier resistance of the gate insulating film 14 can be promoted and insulation resistance can be promoted.

[0099] In forming the silicon oxynitride film, for example, a semiconductor substrate 1 may be subjected to a heat treatment in a nitrogen including gas atmosphere such as NO, NO₂ or NH₃. Further, an effect similar to the above-described can be achieved by forming the gate insulating films 14 comprising silicon oxide at respective surfaces of the p-type well 13P and the n-type well 13N and thereafter subjecting the semiconductor substrate 11S to the heat treatment in the above-described nitrogen gas including atmosphere and segregating nitrogen at an interface of the gate insulating film 14 and the semiconductor substrate 11S.

[0100] Further, the gate insulating film 14 may be formed by, for example, a silicon nitride film or a composite insulating film of a silicon oxide film and a silicon nitride film. When the gate insulating film 14 comprising silicon oxide is thinned to less than 5 nm, particularly, less than 3 nm by a film thickness converted into that of a silicon dioxide film, there is actualized a deterioration in insulation resistance directly by generating tunnel current or hot carriers caused by stress. The silicon nitride film is provided with a dielectric constant higher than that of the silicon oxide film and accordingly, the silicon dioxide conversion film thickness becomes thinner than an actual film thickness. That is, in the case of providing the silicon nitride film, even when the silicon nitride film is physically thick, there can be provided a capacitance equivalent to that of the relatively thin silicon dioxide film. Therefore, by constituting the gate insulating film 14 by a single silicon nitride film or a composite film of silicon nitride and silicon oxide, the effective film thickness can be made thicker than that of the gate insulating film constituted by a silicon oxide film and accordingly, there can be improved a deterioration in insulation resistance by generation of tunnel leakage current or hot carriers.

[0101] In this case, the silicon dioxide conversion film thickness (hereinafter, simply referred to as converted film thickness) dr of a single insulating film or a composite insulating film, is a film thickness defined by the following equation when a specific dielectric constant of an insulating film constituting an object is designated by notation εi, a film thickness thereof is designated by notation di and a specific dielectric constant of silicon dioxide is designated by εs. ${dr} = {\sum{\frac{ɛ\quad i}{ɛ\quad s}{di}}}$

[0102] For example, dielectric constants of silicon oxide (SiO₂) and silicon nitride (Si₃N₄) are respectively 4 through 4.2 and 8. Hence, by carrying out a calculation by making the dielectric constant of silicon nitride as twice as much as the dielectric constant of silicon oxide, for example, the silicon dioxide conversion film thickness of the silicon nitride film having a film thickness of 6 nm becomes 3 nm. That is, capacitance of the gate insulating film comprising a composite film having the silicon nitride film having the film thickness of 6 nm is equal to that of the gate insulating film comprising the silicon oxide film having the film thickness of 3 nm. Further, capacitance of the gate insulating film comprising the silicon oxide film having the film thickness of 2 nm and the silicon nitride film having the film thickness of 2 nm (converted film thickness=1 nm), is the same as capacitance of the gate insulating film comprising a single silicon oxide film having the film thickness of 3 nm.

[0103] Successively, as shown by FIGS. 4A and 4B, a gate electrode forming film 15 is formed by successively depositing a polycrystal silicon layer 15 a, an SiGe layer 15 b and a polycrystal silicon layer 15 c over the semiconductor substrate 11S from lower layers by a CVD process.

[0104] The polycrystal silicon layer 15 a is provided with a function of assisting to form the SiGe layer 15 b without effecting influence on electric properties. That is, the polycrystal silicon layer 15 a assists to form nuclei at an initial stage of film formation in forming the SiGe layer 15 b thereabove and forms the SiGe layer 15 b having a uniform thickness. When there is not the polycrystal silicon layer 15 a, nuclei formation at the initial stage of film formation of the SiGe layer 15 b is difficult to carry out and irregularities of the SiGe layer 15 b are enlarged. The thickness of the polycrystal silicon layer 15 a is, for example, about 3 nm.

[0105] The SiGe layer 15 b is deposited over the polycrystal silicon layer 15 a. The thickness of the SiGe layer 15 b is, for example, about 100 through 200 nm. Further, according to a composition of the SiGe layer 15 b, a concentration of Ge is made to be equal to or larger than 10% of a total. The higher the concentration of Ge of the SiGe layer 15 b, the more preferable. This is, for example, from the following reason. Boron is introduced to the SiGe layer 15 b to reduce the resistance and set the work function to a predetermined value and when the concentration of Ge of the SiGe layer 15 b is high, a concentration of boron can be reduced and therefore, boron depletion can be restrained and vacancy formation caused by boron depletion can be restrained or prevented. The reason of capable of reducing the concentration of boron resides in that when the concentration of Ge of the SiGe layer 15 b is high, the activation efficiency of boron can be promoted and therefore, even when the concentration of boron is low, the resistance of the SiGe layer 15 b can be reduced. Further, when the concentration of Ge of the SiGe layer 15 b is high, even when the concentration of boron is low, the work function of the SiGe layer 15 b can be made a predetermined value.

[0106] Hence, according to Embodiment 1, the concentration of Ge is made equal to or larger than 20%, preferably, equal to or larger than 40%. As described later, when the concentration of Ge of the SiGe layer 15 b is made high, in postprocessing after patterning the SiGe layer 15 b, there is produced so-to-speak side etching in which side faces of the SiGe layer 15 b are polished, however, according to Embodiment 1, the side etching can be restrained or prevented and therefore, the concentration of Ge can be made high.

[0107] Particularly, in an area in which the concentration of Ge of the SiGe layer 15 b is equal to or larger than 40%, in a CMIS (Complementary MIS) circuit, the gate electrode can be constructed by a single gate electrode structure. That is, when a gate electrode material is constituted by polycrystal silicon, there is a case of adopting so-to-speak dual gate electrode structure in which a gate electrode of nMIS of the CMOS circuit is constituted by n-type polycrystal silicon by introducing phosphor and a gate electrode of pMIS is constituted by p-type polycrystal silicon by introducing boron. According to the structure, a reduction in threshold voltage of nMIS and pMIS can be prevented by changing the work function of the gate electrode in accordance with nMIS and pMIS without increasing the concentration of impurity of the semiconductor substrate. However, phosphor and boron are selectively introduced with different photoresist films as masks and accordingly, fabrication steps become complicated, further, a number of fabrication steps is increased and accordingly, an increase in cost of product is brought about. Further, in patterning a gate electrode by an etching processing, an impurity included in a gate electrode portion differs by nMIS and pMIS and accordingly, there is produced a difference in the shape of the gate electrode, a dispersion is caused in dimensions of fabricating the gate electrode and accuracy of fabrication dimensions is deteriorated.

[0108] In contrast thereto, according to Embodiment 1, by making the concentration of Ge of the SiGe layer 15 b equal to or larger than 40%, the work function of the SiGe layer 15 b can easily be set to a value between work function of n-type polycrystal silicon (about 4.15 V) and work function of p-type polycrystal silicon (about 5.15 V) by introducing boron. Therefore, it is not necessary to introduce two kinds of impurities of phosphor and boron to the gate electrode. That is, the gate electrodes of both of NMIS and pMIS can be constructed by a p-type single gate electrode structure introducing only boron. Therefore, according to Embodiment 1, a reduction in threshold voltage of nMIS and pMIS constituting the CMOS circuit can be prevented without increasing the concentration of the impurity of the semiconductor substrate 11S. Further, fabrication steps of a semiconductor integrated circuit device can be simplified. Further, a number of fabrication steps of a semiconductor integrated circuit device can be reduced. Therefore, development and fabrication time of a semiconductor integrated circuit device can be shortened. Further, cost of a semiconductor integrated circuit device can be reduced. Further, in patterning a gate electrode, it is not necessary to consider a difference in the shape of the gate electrode by nMIS and pMIS, a dispersion in dimensions of fabricating the gate electrode in nMIS and pMIS can be reduced and accordingly, accuracy of dimensions of fabricating the gate electrode can be promoted. Therefore, yield of a semiconductor integrated circuit device can be promoted. Further, performance of a semiconductor integrated circuit device can be promoted.

[0109] The SiGe layer 15 b can be formed by a CVD process using a mixed gas of monosilane (SiH₄) and germane (GeH₄). However, in forming the SiGe layer 15 b, boron may be introduced in situ in forming the SiGe layer by depositing the layer by a CVD process using silane (SiH₄), germane (GeH₄) and diborane (B₂H₆) as source gases.

[0110] The polycrystal silicon layer 15 c is deposited over the SiGe layer 15 b. The polycrystal silicon layer 15 c is provided in consideration of depositing cobalt (Co) and forming a cobalt silicide layer as described later. That is, when Co is formed directly over the SiGe layer 15 b, compatibility is low between SiGe and Co, a resistance value of the gate electrode becomes high and accordingly, the polycrystal silicon layer 15 c is provided to prevent thereof. A thickness of the polycrystal silicon layer 15 c is set such that in removing a mask made of silicon oxide formed over the polycrystal silicon layer 15 c by etching as described later, the polycrystal silicon layer 15 c is not penetrated even by an overetching processing thereof and is made, for example, about 50 nm. This is for preventing the SiGe layer 15 b from being exposed directly to a cleaning solution in a cleaning processing which is carried out after removing the mask by etching.

[0111] Next, as shown by arrow marks of FIG. 4, boron, mentioned above, is introduced to the gate electrode forming film 15 by an ion implantation process. As described above, according to the SiGe layer 15 b having the concentration of Ge equal to or larger than 40%, there is constructed a single gate electrode structure of only boron. Further, when boron is introduced in situ in forming the SiGe layer 15 b as described above, it is not necessary to ion-implant boron again.

[0112] Successively, as shown by FIGS. 5A and 5B, an insulating film 16 comprising, for example, a silicon oxide film is formed over the polycrystal silicon layer 15 c by a CVD process. The insulating film 16 constitutes a mask in patterning a gate electrode forming film by a dry etching process. A film thickness of the insulating film 16 needs to set to a sufficient thickness such that when the SiGe layer 15 b is etched, a matrix thereof is not etched and is, for example, about 50 nm.

[0113] Thereafter, after coating a reflection preventive film 17 having a thickness of, for example, 0.1 μm over the insulating film 16, a photoresist pattern 18 having a thickness of, for example, about 0.5 μm is formed thereabove. The photoresist pattern 18 is formed by coating an organic photo resist film over the reflection preventive film 17 and exposing the photoresist film by irradiating the photoresist film with exposure beam such as excimer laser beam via a photomask.

[0114] Next, with the photoresist pattern 18 as an etching mask, the reflection preventive film 17 and the insulating film 16 exposed therefrom are etched and removed by a dry etching process. In this case, in etching processing of the reflection preventive film 17 and the insulating film 16, there is used, for example, an etching apparatus of a parallel flat plate type and the reflection preventive film 17 and the insulating film 16 are processed to etch by separate chambers.

[0115] In processing to etch the reflection preventive film 17, for example, O_(2/)N₂/CF₄ is used as a process gas. Further, in processing to etch the insulating film 16, for example, C₄F₈/Ar/O₂ is used as a process gas. In processing to etch the insulating film 16, by using a gas having a high carbon rate such as C₄F₈, selectivity of etch rate with respect to the polycrystal silicon layer 15 c of the matrix can be provided and accordingly, an amount of polishing the polycrystal silicon layer 15 c can be reduced.

[0116] Successively, by removing the photoresist pattern 18 and the reflection preventive film 17 by ashing as shown by FIGS. 6A and 6B and thereafter subjecting the semiconductor substrate 11S to wet cleaning processing, polymers produced by the dry etching processing are removed.

[0117] Thereafter, with the insulating film 16 patterned by the dry etching processing as an etching mask, the gate electrode forming film 15 (that is, polycrystal silicon layer 15 a, SiGe layer 15 b and polycrystal silicon layer 15 c) exposed therefrom is etched and removed by a dry etching process.

[0118] The dry etching processing is carried out in the etching chamber 8 at inside of the etching apparatus 1 shown in FIG. 1. In the processing, there are required anisotropic shape (verticalness) and high selectivity with respect to the gate insulating film 14 of the matrix. Therefore, according to Embodiment 1, there is used, for example, a microwave etcher and etching conditions are constituted by, for example, following five stage steps.

[0119] A first step is constituted by a condition nonselective with regard to the silicon oxide film. For example, Cl₂ is used as a process gas and a flow rate thereof is set to, for example, about 80 ml/min. Further, pressure is set to, for example, about 0.4 Pa. Further, a microwave/RF is set to, for example, about 400/80 W. A processing time period is set to, for example, about 5 sec.

[0120] A second step is constituted by a condition mainly for providing stability of electricity discharge. For example, HBr/Cl₂ is used as a process gas and a flow rate thereof is set to, for example, about 90 through 20 ml/min. Further, pressure is set to, for example, about 0.4 Pa. Further, a microwave/RF is set to, for example, about 800/40 W. A processing time period is set to, for example, about 2 sec.

[0121] A third step is constituted by a condition having low selectivity with regard to the silicon oxide film. Up to a thickness position at a middle of the SiGe layer 15 b is etched and removed by the third step. For example, HBr/Cl₂/O₂ is used as a process gas and a flow rate thereof is set to, for example, about 90/20/3ml/min. Further, pressure is set to, for example, about 0.4 Pa. Further, a microwave/RF is set to, for example, about 400/30 (or 40) W. A processing time period is set to, for example, about 30 sec.

[0122] A fourth step is constituted by a condition having high selectivity with respect to the silicon oxide film. By the fourth step, up to the polycrystal silicon layer 15 a of the lowermost layer are all etched and removed (just etching). The just etching, mentioned here, refers to a time point at which the gate insulating film 14 is exposed at a portion thereof excluding stepped portions of the element separating portions 12. For example, HBr/O₂ is used as a process gas and a flow rate thereof is set to, for example, about 74/3ml/min. Further, pressure is set to, for example, about 0.4 Pa. Further, a microwave/RF is set to, for example, about 400/25 W. A processing time period is made up to the just etching. In this case, when HBr/O₂ is used, by detecting SiBr (wavelength=426 nm), further, when Cl₂/O₂ is used, by detecting SiCl (wavelength=391 nm), respective end points can be detected.

[0123] A fifth step is an overetching processing and is constituted by a condition of removing a residue of etching of the polycrystal silicon layers 15 a and 15 b. As a process gas, there is used, for example, HBr/O₂ or Cl₂/O₂ having high selectivity with respect to the silicon oxide film as mentioned above and a flow rate thereof is set to, for example, about 105/8 ml/min. Further, pressure is set to, for example, about 0.6 Pa. Further, a microwave/RF is set to, for example, about 400/45 W. A processing time period is set to, for example, about 30 sec.

[0124] By the processing of etching the gate electrode forming film, as shown by FIGS. 7A and 7B, a gate electrode 15G is formed. After the processing, side faces of the gate electrode 15G are formed substantially orthogonally to the main face of the semiconductor substrate 11S. That is, the side edge is not caused at the side faces of the gate electrode 15G.

[0125] Next, the semiconductor substrate 11S finished with the processings, is taken out from the etching chamber 8 of the etching apparatus 1 of FIG. 1 and is transferred into the postprocessing chamber 9 in a state of maintaining vacuum without exposing the semiconductor substrate 11S to outside air. The object of the postprocessing resides in removing reaction products (SiCl, SiOCl, SiOBr) including Si produced in the processing of etching the gate electrode forming film 15 and removing Cl, Br adsorbed to the surface of the semiconductor substrate 11S or reaction products including Cl, Br.

[0126] When the postprocessing is not carried out, reaction products (particularly reaction products including Si) cannot be removed only by a cleaning processing thereafter and therefore, in later steps, the reaction products are exfoliated to thereby produce foreign matters. Further, when the semiconductor substrate 11S after finishing with the etching processing is returned to a wafer cassette, the reaction products are adhered to a main face of other semiconductor substrate 11S before the etching processing and when there is carried out etching processing of the gate electrode forming film with respect to the other semiconductor substrate 11S, the adhered matters constitute a mask to thereby produce residue of etching.

[0127] Further, when Cl or Br adhered to the surface of the semiconductor substrate 11S is not removed, parts of the etching apparatus are corroded by Cl or Br. Further, Cl or Br is provided with high toxicity and accordingly, adverse influence is effected on the human body. Therefore, the postprocessing after the etching processing is indispensable. Even when polycrystal silicon is used as the gate electrode material, the post processing is carried out and, for example, O₂/CHF₃ is used as a process gas in that case.

[0128] Hence, also when the SiGe layer is provided as the gate electrode material, the postprocessing is carried out under the same conditions. That is, similar to the postprocessing when polycrystal silicon is used as a gate electrode material, the postprocessing is carried out by using, for example, O₂/CHF₃ gas. The O₂/CHF₃ gas is used in the post processing because a stable electricity discharge range is provided and further, the gas is generally used in the postprocessing when polycrystal silicon is used as the gate electrode material and is easy to introduce since data amount is enormous.

[0129] As a result, as shown by FIGS. 8A and 8B, it has been found by the inventors for the first time that there is caused side etching of polishing two side faces of the SiGe layer 15 b toward center. Further, an explanation will be given of an amount of side etching in the specification in reference to FIGS. 8A and 8B as follows. That is, a side etching amount (LS1+LS2) is a value produced by subtracting a length LB in a channel direction of the SiGe layer 15 b from a length LA in the channel direction (direction along main face of semiconductor substrate 11S) of the polycrystal silicon layers 15 a and 15 c of the gate electrode 15G (LS1+LS2=(LA−LB)). Here, when the side etching amount is defined by a rate with respect to the length in the channel direction of the remaining polycrystal silicon layers 15 a and 15 b, the side etching amount can be represented by ((LA−LB)/LA)×100(%). In FIGS. 8A and 8B, the side etching amount is about 70% (that is, 70% is polished).

[0130]FIGS. 8A and 8B show a case in which the Ge concentration of the SiGe layer 15 b is made, for example, 50%. As detailed postprocessing conditions, for example, O₂/CHF₃=600/40 (ml/min), pressure is set to 100 Pa, microwave power is set to 1000 W and electricity discharge time is set to 20 sec.

[0131] Further, although the inventors have carried out the postprocessing under the postprocessing condition by a condition of reducing an O₂ flow rate, for example, O₂/CHF₃=100/10 (ml/min), the side etching is caused even in that case. That is, it has been found that the side etching cannot be prevented only by reducing the O₂ amount.

[0132] However, the side etching is not caused under a condition of single O₂ gas. This is because etching of Si is not progressed since there is not a fluorine species gas. However, the adhered matters on the surface of the semiconductor substrate cannot be removed only by O₂ and accordingly, the condition cannot be used in the actual process.

[0133] Further, the side etching is caused even under a condition of adding a very small amount of CHF₃ to O₂, for example, a condition of O₂/CHF₃=600/10 (ml/min). Further, by experiment by the inventors, when the Ge concentration of the SiGe layer is 20%, the side etching is not caused.

[0134] After a result of an investigation based on the result of experiment, the inventors have found for the first time that there is conceivable a model in which when O₂/CHF₃ is used for the post processing condition, O and Ge are explosively reacted with each other in plasma and highly volatile GeO is produced (and accordingly, when the Ge concentration is increased, the side edge amount is increased), as a result, the side etching is caused.

[0135] Hence, according to Embodiment 1, as the postprocessing condition, plasma processing is carried out under a mixed gas atmosphere of a gas hardly reactive to Ge and a gas having an etching function of Si. As a gas hardly reactive to Ge, there is used an inert gas such as argon (Ar) gas further, as a gas having the function of etching Si, there is used a gas including fluorine such as CHF₃.

[0136] As a result, as shown by FIGS. 9A and 9B, a vertical shape of the side faces of the gate electrode 15 can be achieved. Although FIGS. 9A and 9B exemplify a case of causing more or less side etching, according to the post processing condition, the gate electrode 15G can be formed also in a state of dispensing with the side etching. Further, a time period of the postprocessing in this case, is set such that an amount of polishing the polycrystal silicon layer 15 c is set to be substantially in line with the O₂/CHF₃ condition and it is not that the side etching is not caused because the etching amount is small.

[0137] An example of specific postprocessing conditions is shown as follows. That is, for example, Ar/CHF₃ is about 400/20 (ml/min), pressure is about 70 Pa, a microwave power is about 750 W and an electricity discharge time period is about 20 sec. Further, the Ge concentration of the SiGe layer 15 b is, for example, equal to or larger than 20%. According to a result of experiment by the inventors, under a condition of high concentration of CHF₃ in the postprocessing, for example, under a condition of Ar/CHF₃=600/40 (ml/min), for example, there causes deposition of a compound including Si, H (hydrogen) and F (fluorine) and the etching is not progressed and therefore, the concentration of CHF₃ is pertinently equal to or lower than about 5%. Further, in comparison with O₂/CHF₃ condition, Ar/CHF₃ is provided with a narrow electricity discharge stabilized region and electricity discharge becomes unstable under a condition in which pressure is equal to or higher than 80 Pa or the microwave power is equal to or larger than 1000 W. Therefore, from the above-described conditions, it is preferable as the postprocessing conditions that the concentration of CHF₃ is about 5%, pressure is equal to or lower than 70 Pa and the microwave power is about 750 W.

[0138] Further, although according to the above-described postprocessing conditions, as a gas hardly reactive to Ge, there is used Ar having high electricity discharge stability, the gas is not limited thereto but can be changed variously, in place of Ar, for example, there can also be used other inert gas such as helium (He), neon (Ne), krypton (Kr) or xenon (Xe). Further, nitrogen (N₂) gas can also be used in place of Ar. In that case, as a result of forming a silicon nitride (SiN) film at surfaces (side faces or upper face) of the gate electrode in the postprocessing, the SiN film becomes a protective film and functions to prevent side etching of two side faces of the gate electrode.

[0139] Further, although CHF₃ is used as a gas having a function of etching Si, the gas is not limited thereto but can be changed variously and in place of CHF₃, there can also be used a gas including fluorine such as CF₄° C₂F₆ or SF₆. Under a condition of postprocessing gas of Ar/CF₄, an etching rate of the polycrystal silicon layers 15 a and 15 c is large. For example, the etching rate of Ar/CF₄=400/40 (ml/min) is about nine times as much as that of Ar/CHF₃. Hence, in this case, the postprocessing time period is shortened to, for example, about 5 sec. In this case, the side etching amount is larger than that of Ar/CHF₃ to be about 20%, however, side etching under the condition of O₂/CHF₃ is not caused. That is, the side etching amount is about 20% in a gas system of Ar/CF₄ having comparatively large side etching. In this way, according to the invention, the side etching amount can be made equal to or lower than 40%, the side etching amount can be made about 20% as an actually provided result when Ar/CF₄ gas is used and the side etching amount can be made equal to or lower than 10% as an actually provided result when Ar/CHF₃ gas is used.

[0140] In this way, according to Embodiment 1, even after the postprocessing, the sectional shape of the gate electrode 15G having the SiGe layer 15 b can be improved. That is, accuracy of dimensions of fabricating the gate electrode 15G can be promoted. Therefore, according to Embodiment 1, the yield of the semiconductor integrated circuit device can be promoted. Further, the performance of the semiconductor integrated circuit device can be promoted.

[0141] Further, FIG. 10 shows a result of investigating performance of removing Cl or Br adhered to the semiconductor substrate 11S by total reflection fluorescent X-ray. Notations A1 through A3 of the abscissa of FIG. 10 indicate a case of using Ar/CHF₃ as a postprocessing gas (present invention), notation A1 shows a case of the postprocessing time period of 10 sec, notation A2 designates a case of the postprocessing time period of 20 sec and notation A3 designates a case of the postprocessing time period of 25 sec. Further, notation B designates a case of using Ar/CF₄ as a postprocessing gas (present invention) and is a case of the postprocessing time period of 5 sec. Further, notation C designates a case of using O₂/CHF₃ as the postprocessing gas condition (technology investigated by the inventors) and the postprocessing time period is 20 sec. Notation D designates a case in which the postprocessing is not carried out and notation E designates a case in which patterning and postprocessing of the gate electrode are not carried out. It is apparent from FIG. 10 that under the Ar/CHF₃ condition, with regard to the performance of removing Cl and Br, there is achieved an effect equal to or higher than the O₂/CHF₃ condition. After the above-described postprocessing, the semiconductor substrate 11S is taken out from the etching apparatus 1 shown in FIG. 1.

[0142] Next, as shown by FIGS. 11A and 11B, by ion-implanting, for example, phosphor to nMIS forming areas with the gate electrode 15G as a mask, there are formed n⁻-type semiconductor areas 19 a having a low concentration of impurity constituting a source and a drain (LDD; Lightly Doped Drain) of nMIS. Successively, by ion-implanting, for example, boron to pMIS forming areas with the gate electrode 15G as a mask, there are formed p⁻-type semiconductor areas 20 a having a low concentration of impurity constituting a source and a drain (LDD) of pMIS.

[0143] Successively, after depositing an insulating film made of, for example, silicon oxide over the semiconductor substrate 11S by a CVD process, the deposit is etched back by anisotropic dry etching. At this occasion, the insulating film 16 is also etched back and the polycrystal silicon layer 15 c is exposed. In this way, as shown by FIGS. 12A and 12B, there are formed side walls (side wall insulating films) 21 at both side faces of the gate electrode 15G.

[0144] Thereafter, as shown by FIGS. 13A and 13B, by ion-implanting, for example, phosphor to the nMIS forming areas with the gate electrode 15G and the side walls 21 as masks, there are formed n⁺-type semiconductor areas 19 b having a high concentration of impurity constituting the source and the drain of nMIS. Successively, by ion-implanting, for example, boron to the pMIS forming areas with the gate electrode 15G and the side walls 21 as masks, there are formed p⁺-type semiconductor areas 20 b having a high concentration of impurity constituting the source and the drain of pMIS. By the steps up thereto, there are substantially finished nMISQn and pMISQp each having the source and the drain of the LDD structure.

[0145] Next, by depositing, for example, cobalt (Co) over the semiconductor substrate 11S by a sputtering process and carrying out a heat treatment, at interface portions in contact with a Co layer and the semiconductor substrate 11S and the polycrystal silicon layer 15 c, there are formed silicide layers 22 made of, for example, cobalt silicide (CoSi_(x)) (silicide process) as shown in FIG. 14. By forming such silicide layers 22, contact resistance between wirings and the n⁺-type semiconductor areas 19 b, the p⁺-type semiconductor areas 20 b and the gate electrodes 15G can be reduced. Further, parasitic capacitance can be reduced. Therefore, increase of operational speed of the semiconductor integrated circuit device having very small elements (nMISQn, pMISQp) can be promoted. Further, in place of the cobalt silicide layer, a tungsten silicide layer or a titanium silicide layer can also be constituted.

[0146] Successively, as shown by FIG. 15, after depositing an insulating film 23 a comprising, for example, a silicon oxide film over the semiconductor substrate 11S by a CVD process, there are perforated contact holes 24 in the insulating film 23 a to expose the silicide layers 22. Thereafter, by depositing, for example, tungsten or titanium nitride (TiN) over the semiconductor substrate 11S by sputtering process and thereafter depositing, for example, tungsten thereabove by a CVD process and polishing the conductive films by a CMP (Chemical Mechanical Polish) process such that the conductive films remain only in the contact holes 24, plugs 25 a are formed in the contact holes 24.

[0147] Next, by depositing, for example, titanium nitride, aluminum (or aluminum alloy) and titanium nitoride over the insulating film 23 a and the plugs 25 a successively from lower layers by a sputtering process, and thereafter patterning thereof by normal photolithography technology and dry etching technology, first layer wirings 26 a are formed.

[0148] Successively, after depositing an insulating film 23 b comprising, for example, a silicon oxide film over the insulating film 23 a by a CVD process, there are perforated through holes 27 such that portions of the first layer wirings 26 a are exposed in the insulating film 23 b. Thereafter, after forming plugs 25 b in the through holes 27 similar to the plugs 25 a, second layer wirings 26 b are formed over the insulating film 23 b similar to the first layer wirings 26 a. Thereafter, by a normal fabrication method of the semiconductor integrated circuit device, there is fabricated the system LSI having a multiple layer wiring structure.

[0149] (Embodiment 2)

[0150] In Embodiment 2, an explanation will be given of a case of applying the invention to a fabrication method of a system LSI having a polymetal gate electrode structure including, for example, an SiGe layer in reference to FIG. 16A through FIG. 22B. Further, FIG. 16B through FIG. 22B are sectional views enlarging essential portions of nMIS forming areas of FIGS. 16A through 22A. Also in this case, a gate electrode structure of a pMIS forming area is the same as a gate electrode structure of an nMIS forming area and accordingly, illustration thereof is omitted.

[0151] First, after having been processed at the steps of FIG. 2 and FIG. 3 used in Embodiment 1, as shown by FIGS. 16A and 16B, similar to Embodiment 1, the gate insulating time 14 is formed over the main face of the semiconductor substrate 11S. Successively, similar to Embodiment 1, the polycrystal silicon layer 15 a and the SiGe layer 15 b are deposited over the semiconductor substrate 11S successively from the lower layer. Thereafter, as shown by arrow marks of FIGS. 16A and 16B, similar to Embodiment 1, boron, mentioned above, is introduced to the SiGe layer 15 b by an ion implantation process. As described above, also in Embodiment 2, in the SiGe layer 15 b having the concentration of Ge equal to or larger than 40%, there is constructed the single gate electrode structure only of boron. Further, as described above, when boron is introduced in situ in forming the SiGe layer 15 b, it is not necessary to ion-implant boron again.

[0152] Next, as shown by FIGS. 17A and 17B, in order to constitute a polymetal gate electrode structure, by depositing a barrier conductor layer 15 d having a thickness of, for example, about 5 nm and made of tungsten nitride (WN) or titanium nitride (TiN) over the SiGe layer 15 b by a sputtering process and thereafter depositing a metal layer 15 e having a thickness of, for example, about 80 nm and made of tungsten (W) or molybdenum (Mo) thereabove, the gate electrode forming film 15 is formed. The barrier conductive layer 15 d is provided for, for example, stress relaxation and adherence promotion of the SiGe layer 15 b and the metal layer 15 e.

[0153] Successively, there is formed an insulating film 28 comprising, for example, a silicon nitride film (Si₃N₄) over the metal layer 15 e. In this case, the insulating film 28 is constituted by depositing a silicon nitride film formed by a thermal CVD process over a silicon nitride film formed by a plasma CVD process. This is because the etching rate is lower in the silicon nitride film by the thermal CVD process than in the silicon nitride film by the plasma CVD process (selection ratio with regard to silicon oxide film is made higher). That is, in forming contact holes in later steps, even when the insulating film 28 is exposed from the contact holes, the insulating film 28 is prevented from being etched and removed.

[0154] Thereafter, after forming the reflection preventive film 17 and the photoresist pattern 18 over the insulating film 28 similar to Embodiment 1, with the photoresist pattern 18 as an etching mask, the reflection preventive film 17 and the insulating film 28 exposed therefrom are etched and removed by a dry etching process. In this case, in processing to etch the reflection preventive film 17 and the insulating film 28, there is used, for example, an etching apparatus of a parallel flat plate type and the reflection preventive film 17 and the insulating film 28 are processed to etch by separate chambers. In processing to etch the insulating film 28, there is used, for example, CF₄/Ar as process gas.

[0155] Next, similar to Embodiment 1, after removing the photoresist pattern 18 and the reflection preventive film 17 by ashing as shown by FIGS. 18A and 18B, subjecting the semiconductor substrate 11S to a wet cleaning processing and removing polymers produced by the dry etching processing, with the insulating film 28 patterned by the dry etching processing as an etching mask, the gate electrode forming film 15 (that is, metal layer 15 e, barrier conductor layer 15 d, SiGe layer 15 b and polycrystal silicon layer 15 a) exposed therefrom is etched and removed by a dry etching processing.

[0156] The dry etching processing is carried out in the etching chamber 8 at inside of the etching apparatus 1 shown in FIG. 1. In processing to etch the metal layer 15 e and the barrier conductor layer 15 d, there is carried out an etching processing at an elevated temperature (for example, about 100 through 150° C.) using, for example, Cl/O₂ gas or an etching processing at normal temperature using, for example, CF₄/O₂/N₂/Cl₂ gas. An etching processing of the SiGe layer 15 b and the polycrystal silicon layer 15 a is the same as that in Embodiment 1 and therefore, an explanation thereof will be omitted.

[0157] By the etching processing of the gate electrode forming film 15, as shown by FIGS. 19A and 19B, there is formed the gate electrode 15G of a polymetal structure having the metal layer 15 e over the SiGe layer 15 b. Also after the processing, the side faces of the gate electrode 15G are formed substantially orthogonal to the main face of the semiconductor substrate 11S. That is, the side etching is not caused at the side faces of the gate electrode 15G.

[0158] Next, the semiconductor substrate 11S finished with the processings is transferred into the postprocessing chamber 9 similar to Embodiment 1 and is subjected to a postprocessing similar to that in Embodiment 1. Thereby, as shown by FIGS. 20A and 20B, the vertical shape of the side faces of the gate electrode 15 having the polymetal structure can be achieved. Although FIG. 20B exemplifies the case of causing more or less side etching, according to the postprocessing conditions, the gate electrode 15G can be formed in a state of dispensing with side etching. After the above-described postprocessing, the semiconductor substrate 11S is taken out from the etching apparatus 1 shown in FIG. 1.

[0159] Successively, as shown by FIGS. 21A and 21B, similar to Embodiment 1, after forming n⁻-type semiconductor areas 19 a having a low concentration of impurity at nMIS forming areas, p⁻-type semiconductor areas 20 a having a low concentration of impurity are formed at pMIS forming areas. Thereafter, after depositing an insulating film made of, for example, silicon nitride over the semiconductor substrate 11S by a CVD process and thereafter etching back thereof by anisotropic etching, there are formed the side walls 21 each comprising a silicon nitride film at the gate electrode 15G and two side faces of the insulating film 28. Thereafter, as shown by FIGS. 22A and 22B, similar to Embodiment 1, after forming n⁺-type semiconductor areas 19 b having a high concentration of impurity at the nMIS forming areas, there are formed p⁺-type semiconductor areas 20 b having a high concentration of impurity at pMIS forming areas. By steps up to this stage, there are substantially completed nMISQn and pMISQp each having the source and the drain of the LDD structure.

[0160] Next, after depositing the insulating film 23 a comprising, for example, a silicon oxide film over the semiconductor substrate 11S by a CVD process, the contact holes 24 are perforated in the insulating film 23 a. At this occasion, the contact holes 24 are formed by carrying out an etching processing under an etching condition in which the silicon oxide film is made to be easier to etch by making an etching selection ratio of the silicon oxide film higher than that of the silicon nitride film. In this case, as shown by FIG. 22B, although the contact hole 24 overlaps the gate electrode 15G more or less in plane view, the gate electrode 15G is not exposed owing to the side wall 21 and the insulating film 28 made of silicon nitride (that is, the contact hole 24 can be formed self-adjustingly with respect to the gate electrode 15G) and accordingly, an integration degree of elements can be promoted.

[0161] Thereafter, there is fabricated a system LSI having a multiple layer wiring structure similar to Embodiment 1.

[0162] An effect similar to that of Embodiment 1 can be achieved also in Embodiment 2.

[0163] Although a specific explanation has been given of the invention carried out by the inventors based on the embodiments as described above, the invention is not limited to the embodiments but can naturally be changed variously within a range not deviated from a gist thereof.

[0164] For example, although in Embodiments 1 and 2, the etching chamber for patterning the gate electrode and the postprocessing chamber are separated from each other, the invention is not limited thereto but the etching processing and the postprocessing can be carried out in the same chamber. In this case, the postprocessing chamber is dispensed with and accordingly, cost of the etching apparatus can be reduced.

[0165] Further, although in Embodiments 1 and 2, an explanation has been given of the case of applying the invention to a fabrication technology of the gate electrode having the SiGe layer, the invention is not limited thereto but the invention is applicable, for example, a fabrication technology of wirings having Ge compounds.

[0166] Further, although in Embodiments 1 and 2, an explanation has been given of the case of forming only the elements having the same thickness of the gate insulating film (SiO₂ converted film thickness), the invention is not limited thereto but the invention is applicable also to the case in which a plurality of elements having different thicknesses of gate insulating films are formed over the same semiconductor substrate. In this case, the film thickness of a gate insulating film of MIS using relatively high power source voltage is made thicker than the film thickness of a gate insulating film of MIS driven by relatively low power source voltage and requesting high-speed operation.

[0167] Although in the above-described explanation, an explanation has been given of the case of applying the invention carried out by the inventors to the fabrication technology of the system LSI which is a field of use constituting the background of the invention, the invention is not limited thereto but the invention is applicable to a semiconductor integrated circuit device having a memory circuit of, for example, DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory) or a flash memory (EEPROM; Electric Erasable and Programmable Read Only Memory) or a semiconductor integrated circuit device having a logic circuit such as a microprocessor.

[0168] A simple explanation will be given of effects achieved by representative aspects of the invention disclosed in the application as follows.

[0169] (1) According to one of the embodiments, by patterning a gate electrode having an SiGe layer and thereafter subjecting a semiconductor substrate to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a second gas having a function of etching Si, a shape of a gate electrode having the SiGe layer can be improved.

[0170] (2) According to one of the embodiments, by patterning the gate electrode having the SiGe layer and thereafter subjecting the semiconductor substrate to the plasma processing in the atmosphere of the mixed gas of the first gas hardly reactive to Ge and second gas having the function of etching Si, accuracy of dimensions of fabricating the gate electrode having the SiGe layer can be promoted.

[0171] (3) By (1) or (2), mentioned above, yield of the semiconductor integrated circuit device having the gate electrode having the SiGe layer can be promoted.

[0172] (4) By (1) or (2), mentioned above, performance of the semiconductor integrated circuit device having the gate electrode having the SiGe layer can be promoted.

[0173] (5) According to one of the embodiments, in a fabrication method of a semiconductor integrated circuit device having n-channel type and p-channel type field effect transistors over a semiconductor substrate, by patterning the gate electrode having the SiGe layer of the respective field effect transistor and thereafter subjecting the semiconductor substrate to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a function of etching Si, development and fabrication time period of the semiconductor integrated device having the gate electrode having the SiGe layer can be shortened.

[0174] (6) According to one of the embodiments, in the fabrication method of the semiconductor integrated circuit device having the n-channel type and the p-channel type field effect transistors over the semiconductor substrate, by patterning the gate electrode having the SiGe layer of the respective field effect transistor and thereafter subjecting the semiconductor substrate to the plasma processing in the atmosphere of the mixed gas of the first gas hardly reactive to Ge and the second gas having the function of etching Si, fabrication steps of the semiconductor integrated circuit device having the gate electrode having the SiGe layer can be simplified. 

What is claimed is:
 1. A semiconductor integrated circuit device comprising: (a) a gate insulating film formed over a main face of a semiconductor substrate; and (b) a gate electrode formed over the gate insulating film, wherein the semiconductor substrate has been subjected to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a second gas having a function of etching Si, after forming the gate electrode, wherein the gate electrode includes an SiGe layer and a polycrystal silicon layer formed at a layer upward therefrom, and wherein a side etching amount at two side faces of the gate electrode is equal to or smaller than 40% of a length in a channel length direction of the polycrystal silicon layer constituting the gate electrode.
 2. A semiconductor integrated circuit device comprising: (a) a gate insulating film formed over a main face of a semiconductor substrate; and (b) a gate electrode formed over the gate insulating film, wherein the semiconductor substrate has been subjected to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a second gas having a function of etching Si, wherein the gate electrode includes an SiGe layer and a polycrystal silicon layer formed at a layer upward therefrom, and wherein a length in a channel length direction of the gate electrode at the SiGe layer, is equal to a length in the channel length direction of the polycrystal silicon layer constituting the gate electrode.
 3. A semiconductor integrated circuit device comprising: (a) a gate insulating film formed over a main face of a semiconductor substrate; and (b) a gate electrode formed over the gate insulating film, wherein the semiconductor substrate has been subjected to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a second gas having a function of etching Si, after forming the gate electrode, wherein the gate electrode includes an SiGe layer and a metal layer formed at a layer upward therefrom, and wherein a side etching amount at two sides faces of the gate electrode is equal to or smaller than 40% of a length in a channel length direction of the metal layer constituting the gate electrode.
 4. A semiconductor integrated circuit device comprising: (a) a gate insulating film formed over a main face of a semiconductor substrate; and (b) a gate electrode formed over the gate insulating film, wherein the semiconductor substrate has been subjected to a plasma processing in an atmosphere of a mixed gas of a first gas hardly reactive to Ge and a second gas having a function of etching Si, after forming the gate electrode, and wherein a length in a channel length direction of the gate electrode at an SiGe layer, is equal to a length in the channel length direction of a metal layer constituting the gate electrode. 